Fusion furnace, gasification fusion furnace, and method of processing waste

ABSTRACT

The slagging combustion furnace ( 10 ) of the present invention includes a combustion chamber ( 11, 12, 13 ) for combusting a combustible gas containing ash and melting the ash, and a slag discharge port ( 17 ) for discharging molten slag ( 20 ) produced by melting the ash. The slag discharge port ( 17 ) is formed by refractory material which is replaceable.

TECHNICAL FIELD

[0001] The present invention relates to a slagging combustion furnaceand a gasification and slagging combustion system for being suppliedwith a gas produced in a gasification furnace or the like and containingash and unburned carbon, and combusting the supplied gas at a hightemperature to melt the ash into molten slag.

BACKGROUND ART

[0002] There has been a demand for incinerating wastes includingmunicipal wastes, industrial wastes, medical wastes, shredder dust,waste tires, and the like to reduce the volume of the wastes, andeffectively utilizing heat of incineration of the wastes. Becauseincineration ash of the wastes normally contains harmful heavy metals,in order to discard the incineration ash in a landfill site, it isnecessary to take some measures for solidifying heavy metal components.Further, there has been a demand for downsizing an overall wastetreatment system. In order to solve the above problems, a gasificationand melting furnace (gasification and slagging combustion system) whichcan recover various metals, melt ash to produce molten slag and recoverthe produced molten slag, and recover energy in the form of heat,electric power or the like has come into the limelight as a wastetreatment system. The gasification and slagging combustion system is nota simple incineration treatment, but is a combination of pyrolysisgasification and high-temperature combustion, and is capable ofperforming material recycling.

[0003]FIG. 1 is a schematic view showing a conventional gasification andslagging combustion system which is a combination of a fluidized-bedgasification furnace and a swirling-type slagging combustion furnace. Asshown in FIG. 1, the gasification and slagging combustion systemcomprises a fluidized-bed gasification furnace 1 and a swirling-typeslagging combustion furnace 10. In the gasification and slaggingcombustion system shown in FIG. 1, wastes are supplied to a fluidizedbed 2 and gasified to produce a combustible gas containing unburnedcarbon and ash and having a temperature of about 500° C. to about 600°C. in the gasification furnace 1, and the produced combustible gas isintroduced into the slagging combustion furnace 10 and combusted by asecondary air at a high temperature under a low air ratio of about 1.3to about 1.5 to increase a temperature of the interior of the furnace toa melting point of ash or higher (for example, 1300° C. or higher,preferably about 1350° C.) in the swirling-type slagging combustionfurnace 10. In this high-temperature condition, ash is collected on awall surface of the furnace, and a flow of molten slag is formed. Themolten slag is discharged through a slag discharge port 17 to theoutside of the furnace. Then, the discharged molten slag is brought intocontact with slag cooling water to form water-quenched slag.

[0004] On the other hand, a high-temperature combustion gas generated inthe process in which ash content is melted to form molten slag isintroduced into a waste heat boiler, a heat exchanger or the like inwhich thermal energy is recovered. In such gasification and slaggingcombustion system, the structure of the slagging combustion furnaceaffects melting state of ash and stable operation of the slaggingcombustion furnace, and hence it has been considered that the structureof the slagging combustion furnace is technically important for theoverall gasification and slagging combustion system.

[0005]FIG. 2 is a schematic view of the conventional slagging combustionfurnace. As shown in FIG. 2, reference numeral 10 represents theslagging combustion furnace 10, and the slagging combustion furnace 10comprises a primary combustion chamber 11, a secondary combustionchamber 12, and a tertiary combustion chamber 13. A passage which isformed within the slagging combustion furnace and allows a combustiongas 16 to pass therethrough comprises a substantially V-shaped passageas shown by the arrow, and a slag discharge port 17 is formed at thelowermost position of the V-shaped passage.

[0006] A produced gas 14 produced by gasification in the gasificationfurnace 1 (see FIG. 1) and containing unburned carbon and ash, or amixed gas of the produced gas 14 and combustion gas is introduced intothe upper part of the primary combustion chamber 11 in a directiontangential to an inner wall surface of the slagging combustion furnace10. Combustion air 15 is also introduced into the primary combustionchamber 11 in a direction tangential to the inner wall surface of theslagging combustion furnace 10. Thus, the produced gas 14 or the mixedgas of the produced gas 14 and the combustion gas is mixed with thecombustion air 15, and is combusted while forming a swirling flow of thegas, and moves to the secondary combustion chamber 12 and is combustedat a high temperature of 1200 to 1400° C., preferably about 1350° C. inthe secondary combustion chamber 12 and then the tertiary combustionchamber 13. Then, exhaust gas 16′ is discharged from the tertiarycombustion chamber 13, and is then introduced into a waste heat boileror the like (not shown in the drawing). In FIG. 2, reference numerals 18and 19 represent an auxiliary burner, respectively. In the aboveexample, both of the produced gas 14 and the combustion air 15 areintroduced in the direction tangential to the inner wall surface of thefurnace. However, one of the produced gas 14 and the combustion air 15may be introduced in a direction tangential to the inner wall surface ofthe furnace to thus generate a swirling flow of the gas, and the otherof the produced gas 14 and the combustion air 15 may be blown into theformed swirling flow, thereby combusting while having mixed with eachother.

[0007] As described above, the produced gas 14 containing unburnedcarbon and ash and the combustion air 15 introduced into the upper partof the primary combustion chamber 11 are mixed with each other whileforming a swirling flow of the gas in the primary combustion chamber 11,and the produced gas 14 is combusted in the primary combustion chamber11, and then moves to the secondary combustion chamber 12 and thetertiary combustion chamber 13. Ash is collected on the inner wallsurface of the furnace due to the swirling flow in the furnace, and ismelted at a high temperature to form molten slag 20. The molten slagflows downwardly on the furnace bottom, and falls down from the slagdischarge port 17 through a slag discharge chute 30 to the outside ofthe furnace. Then, the discharged molten slag 20 is brought into contactwith slag cooling water (not shown in the drawing) to formwater-quenched slag, and the granulated slag is recovered.

[0008]FIG. 3 is a view showing the furnace bottom having the slagdischarge port of the slagging combustion furnace in an example. Asshown in FIG. 3, the molten slag 20 flowing downwardly on the wallsurface of the slagging combustion furnace 10 is collected at thefurnace bottom, and falls down along an inner wall surface 17 a of theslag discharge port 17. Thus, the inner wall surface 17 a of the slagdischarge port 17 is concentratedly exposed to the molten slag 20 havinga high temperature to cause damage of the inner wall surface 17 a due tomelting. When such melting damage progresses, it is necessary to replacethe inner wall of the slag discharge port 17 with a new one. Further,the slag discharge port 17 is a boundary between the high-temperaturesecondary and tertiary combustion chambers 12 and 13, and thelow-temperature slag discharge chute 30 (the slag discharge chute 30 iscooled to a low temperature because slag cooling water is in the lowerpart of the slag discharge chute 30), and hence refractory material issubjected to severe conditions because of the formation of temperaturegradient and is liable to be damaged or broken. However, because theinner wall of the slag discharge port 17 is integrally formed with theinner wall of the slagging combustion furnace 10, the replacement workof the inner wall of the slag discharge port 17 is not easy and istroublesome.

[0009] Alternatively, it may be considered that the inner wall of theslag discharge port 17 is formed by refractory material which isresistant to a thermal wear and a high temperature as preventivemeasures against a thermal wear and a thermal damage. However, becausethe inner wall of the slag discharge port 17 is integrally formed withthe inner wall of the slagging combustion furnace 10, it has beendifficult to form only the inner wall of the slag discharge port 17 byrefractory material which is resistant to a thermal wear and a hightemperature. Further, since the refractory material which is resistantto a thermal wear and a high temperature is expensive, it isuneconomical to form the entire inner wall of the slagging combustionfurnace 10 by the refractory material which is resistant to a thermalwear and a high temperature.

[0010] Further, in order to reduce the amount of thermal wear, watertubes may be provided on the inner wall of the slag discharge port 17.However, in this case, the inner wall surface 17 a of the slag dischargeport 17 is cooled excessively, and hence the molten slag 20 is adheredto the inner wall surface 17 a and solidified thereon to form aggregatedslag 21 as shown in FIG. 3. In the worst case, the slag discharge port17 is clogged with the aggregated slag. Further, in this case, if therefractory material is not dried and burned, the refractory materialdoes not display its innate strength. Therefore, when the refractorymaterial is cooled excessively by the water tubes, the refractorymaterial is liable to be damaged or broken due to a shortage ofstrength.

[0011]FIG. 4 is a second view showing the slag discharge port of theslagging combustion furnace 10 in another example. As shown in FIG. 4,the inner wall of the slag discharge port 17 has the same height in anentire circumference thereof. Specifically, the height h₁ of the innerwall at the upstream side of the flow of the combustion gas 16 is equalto the height h₂ of the inner wall at the downstream side of the flow ofthe combustion gas 16 (h₁=h₂). That is, the upper end of the slagdischarge port 17 is located at the same level, and the upper surface 17b of the furnace bottom at an outer circumferential portion around theslag discharge port 17 is inclined downwardly toward the slag dischargeport 17. Therefore, the combustion gas 16 which flows at the upstreamside of the slag discharge port 17 along the upper surface 17 b at theouter circumferential portion around the slag discharge port 17 collideswith the inner wall surface 17 a of the slag discharge port 17 to thusgenerate a turbulent flow of the gas in the slag discharge port 17. Thisturbulent flow has a bad influence on discharge conditions of the moltenslag discharged through the slag discharge port 17.

[0012] As one of attendant problems, the molten slag 20 is adhered tothe inner wall surface 17 a of the slag discharge port 17 and solidifiedthereon to form aggregated slag 21 (see FIG. 3). In the worst case, theslag discharge port 17 is clogged with the aggregated slag, or thecombustion gas 16 containing harmful components is discharged throughthe slag discharge port 17 to the outside of the slagging combustionfurnace, thus contaminating slag cooling water.

DISCLOSURE OF INVENTION

[0013] The present invention has been made in view of the abovedrawbacks. It is therefore an object of the present invention to providea slagging combustion furnace and a gasification and slagging combustionsystem which allows an inner wall of a slag discharge port to bereplaced easily with a new one if the inner wall of the slag dischargeport is damaged by melting, allows the inner wall of the slag dischargeport to be less susceptible to a thermal wear or a breakage, and canprevent molten slag from being adhered to the inner wall of the slagdischarge port or being solidified thereon due to an excessive coolingof the slag discharge port.

[0014] Another object of the present invention is to provide a slaggingcombustion furnace and a gasification and slagging combustion system inwhich a turbulent flow of the gas is not generated in the slag dischargeport of the slagging combustion furnace and discharge conditions of themolten slag are not affected.

[0015] Still another object of the present invention is to provide aslagging combustion furnace and a gasification and slagging combustionsystem which allows adhesion or solidification of the molten slag at theslag discharge port to be detected, can prevent the slag discharge portfrom being clogged, or can dissolve clogging of the slag discharge port.

[0016] In order to achieve the above object of the present invention,according to an aspect of the present invention, there is provided aslagging combustion furnace comprising: a combustion chamber forcombusting a combustible gas containing ash and melting the ash; and aslag discharge port for discharging molten slag produced by melting theash; wherein the slag discharge port is formed by refractory materialwhich is replaceable.

[0017] With the above arrangement, because a slag discharge port isformed by a replaceable slag discharge port block which is a distinctmember different from a furnace wall of a slagging combustion furnace,the slag discharge port block can be produced in advance usingrefractory material having a high resistance to a thermal wear and ahigh temperature through a predetermined manufacturing process (forexample, a forming process and a drying process) in a plant. Thus, thenewly produced slag discharge port block is carried into the site wherethe slagging combustion furnace is placed, and the slag discharge portblock which has been damaged by melting or broken for some cause can beeasily replaced with the newly produced slag discharge port block.Further, since the slag discharge port block is composed of refractorymaterial (for example, high chromium refractory material) which isresistant to a thermal wear and a high temperature, the wall of the slagdischarge port can be prevented from thermal wear or breakage. Further,since the portion around the slag discharge port is formed by the slagdischarge port block, the slag discharge port is not cooled excessivelybecause the refractory material is not required to be cooled or slightcooling of the refractory material is sufficient by water tubes, unlikea conventional discharge port, thus preventing molten slag from beingadhered to the inner wall of the slag discharge port or being solidifiedthereon.

[0018] According to one aspect of the present invention, the slagdischarge port comprises an opening formed at a central portion of aslag discharge port block, and at least one slag discharge grooveextending from an outer peripheral portion of the slag discharge portblock at the upstream side of a flow of combustion gas to the slagdischarge port is formed in an upper surface of the slag discharge portblock.

[0019] With the above arrangement, because a slag discharge grooveextending from an outer periphery of the slag discharge port block at anupstream side of a combustion gas passage to the slag discharge port isformed in an upper surface of the slag discharge port block, molten slagflowing downwardly on the inner wall surface of the slagging combustionfurnace flows through the slag discharge groove into the slag dischargeport, and falls down through the slag discharge port. Thus, thedischarge position of the molten slag is fixed. Further, since themolten slag flows concentratedly, even if the scale of system oroperational condition of the system is such that the amount of slag tobe generated is small, the molten slag is less susceptible to beingcooled. Thus, the molten slag is prevented from being adhered to thesurface of the slag discharge port block or being solidified thereon.

[0020] According to one aspect of the present invention, the uppersurface of the slag discharge port block is a slant surface which isinclined downwardly toward the slag discharge port, and an upper end ofan outer wall forming the slag discharge port at the upstream side ofthe flow of the combustion gas is higher than an upper end of the innerwall forming the slag discharge port at the downstream side of the flowof the combustion gas.

[0021] With the above arrangement, because the upper surface of the slagdischarge port block is formed into a slant surface which is inclineddownwardly toward the slag discharge port, and the height of the innerwall of the slag discharge port at the upstream side of a flow of thecombustion gas is higher than the height of the inner wall of the slagdischarge port at the downstream side of the flow of the combustion gas,the combustion gas which has flowed into the upper surface of the slagdischarge port block at the upstream side of the flow of the combustiongas passes through a location above the slag discharge port, and flowsalong the upper surface of the slag discharge port at the downstreamside of the slag discharge port. Thus, since the combustion gas does notcollide with the inner wall surface of the slag discharge port, thecombustion gas can be prevented from flowing into the slag dischargeport. Further, the gas flow near the slag discharge port is smoothed,and hence a fall position of the discharged molten slag is not deviated.If this deviation is large, the slag is attached to the inner surface ofthe slag discharge chute.

[0022] According to one aspect of the present invention, the uppersurface of the slag discharge port block is a slant surface which isinclined downwardly toward an outer circumferential portion of the slagdischarge port block.

[0023] Because the upper surface of the slag discharge port block isformed into a slant surface which is inclined downwardly toward theouter periphery of the slag discharge port block, the combustion gaswhich has flowed into the upper surface of the slag discharge port blockat the upstream side of the flow of the combustion gas moves toward theslag discharge port in an upward flow. Thus, the combustion gas isprevented from flowing into the slag discharge port. Further, becausethe upper surface of the slag discharge port block is formed into theslant surface which is inclined downwardly toward the outer periphery ofthe slag discharge port block, molten slag attached to the upper surfaceis entirely collected at the outer circumferential portion, and moltenslag flowing downwardly on the inner wall surface of the slaggingcombustion furnace is collected at the outer circumferential portion ofthe slag discharge port block. Then, the molten slag flows through theslag discharge groove into the slag discharge port, and falls downthrough the slag discharge port. Thus, the molten slag is prevented frombeing adhered to the surface of the slag discharge port block or beingsolidified thereon.

[0024] According to one aspect of the present invention, the slagdischarge port block comprises a plurality of block pieces.

[0025] With the above arrangement, since the slag discharge port blockis composed of a plurality of block pieces, the slag discharge portblock can be easily produced and can be easily transported. Further,even if the slag discharge port block is damaged or broken, only theblock piece which has been damaged or broken can be replaced. Thus, thereplacement of the block piece is facilitated.

[0026] According to the present invention, there is provided agasification and slagging combustion system, comprising: a gasificationfurnace for gasifying wastes to produce a combustible gas containing theash and the unburned carbon; and a slagging combustion furnace forcombusting the combustible gas containing ash and unburned carbon andmelting the ash; the slagging combustion furnace comprising any one ofthe above slagging combustion furnaces.

[0027] As described above, as a slagging combustion furnace of agasification and slagging combustion system, by using any of the aboveslagging combustion furnaces, the slagging combustion furnace whichexhibits the above features and good operational efficiency can beconstructed.

[0028] Further, in order to solve the above problems, according toanother aspect of the present invention, there is provided a slaggingcombustion furnace comprising: a combustion chamber for combusting acombustible gas containing ash and melting the ash; and a slag dischargeport for discharging molten slag produced by melting the ash; whereinthe height of an inner wall forming the slag discharge port is higher atthe upstream side of a flow of combustion gas than at the downstreamside of the flow of the combustion gas.

[0029] With the above arrangement, because the height of the inner wallof the slag discharge port at the upstream side of the flow of thecombustion gas is higher than the height of the inner wall of the slagdischarge port at the downstream side of the flow of the combustion gas,the combustion gas which has flowed along the upper surface at theupstream side of the slag discharge port passes through a location abovethe slag discharge port, and reaches the upper surface at the downstreamside of the slag discharge port. Thus, since the combustion gas flowssmoothly without causing the combustion gas to collide with the innerwall of the slag discharge port and without generating a turbulent flowat the location near the slag discharge port, unlike the conventional,the flow of the combustion gas does not affect adversely the dischargestate of the molten slag. Because the combustion gas passes through alocation above the slag discharge port, and a flow direction of thecombustion gas is changed by the upper surface at the downstream side ofthe slag discharge port, the amount of the combustion gas flowing intothe slag discharge port can be greatly reduced.

[0030] According to one aspect of the present invention, an uppersurface at an outer circumferential portion around the slag dischargeport is a slant surface inclined upwardly toward the slag dischargeport, and at least one slag discharge groove extending to the slagdischarge port is formed in the slant surface at the upstream side ofthe flow of the combustion gas.

[0031] With the above arrangement, because the upper surface at an outercircumferential portion around the slag discharge port is formed into aslant surface which is inclined upwardly toward the slag discharge port,and the height of the inner wall of the slag discharge port and theinclination angle of the slant surface at the upstream side of the flowof the combustion gas are set such that the combustion gas flowing alongthe slant surface at the upstream side reaches the slant surface at thedownstream side, the combustion gas which has flowed into the uppersurface at the upstream side of the slag discharge port passes though alocation above the slag discharge port, and reaches the upper surface atthe downstream side of the slag discharge port. Thus, since thecombustion gas flows smoothly without causing the combustion gas tocollide with the inner wall of the slag discharge port and withoutgenerating a turbulent flow at the location near the slag dischargeport, the flow of the combustion gas does not affect adversely thedischarge state of the molten slag.

[0032] Because the upper surface at an outer circumferential portionaround the slag discharge port is formed into a slant surface which isinclined upwardly toward the slag discharge port, the combustion gaswhich has flowed into the upper surface at the upstream side of the slagdischarge port moves toward the slag discharge port in an upward flow.Thus, the combustion gas is prevented from flowing into the slagdischarge port.

[0033] Because a slag discharge groove extending from a slant surface atthe upstream side of the combustion gas passage to the slag dischargeport is formed in the upper surface at an outer circumferential portionaround the slag discharge port, molten slag flowing downwardly on theinner wall of the slagging combustion furnace flows through the slagdischarge groove into the slag discharge port. Thus, the dischargeposition of the molten slag is fixed. Because molten slag flowsconcentratedly through a slag discharge groove, even if the scale ofsystem or operational condition of the system is such that the amount ofslag to be generated is small, the molten slag is less susceptible tobeing cooled. Thus, the molten slag is prevented from being adhered tothe surface of the radially outer portion of the slag discharge port orbeing solidified thereon.

[0034] According to one aspect of the present invention, there isprovided a waste treatment method comprising: gasifying wastes toproduce a combustible gas containing ash in a fluidized-bed furnace;combusting the combustible gas and melting the ash to form molten slagin a slagging combustion furnace, the slagging combustion furnacecomprising a primary combustion chamber, a secondary combustion chamberand a tertiary combustion chamber; trapping the molten slag on an innerwall surface of the primary combustion chamber and flowing the trappedmolten slag downwardly into the secondary combustion chamber; flowingthe molten slag on the inner wall surface of the secondary combustionchamber and discharging the molten slag through a slag discharge grooveformed in a slag discharge port block to a slag discharge port formed inthe slag discharge port block, the slag discharge port block beingdisposed at a lowermost part of the secondary combustion chamber, theslag discharge groove being formed at the primary combustion chamberside; trapping molten slag on an inner wall surface of the tertiarycombustion chamber from combustion gas introduced into the tertiarycombustion chamber, and then discharging the trapped molten slag throughthe slag discharge groove to the slag discharge port block; andsupplying the molten slag discharged from the slag discharge groove to awater quenching trough and cooling the discharged molten slag in thewater quenching trough.

[0035] According to the present invention, because a slag dischargegroove is formed only at the primary combustion chamber side, the moltenslag is concentratedly discharged through the slag discharge groove andpart of combustion gas flows through the slag discharge groove toprevent the slag from being cooled.

[0036] According to another aspect of the present invention, there isprovided a waste treatment method comprising: gasifying wastes toproduce a combustible gas containing ash in a fluidized-bed furnace;combusting the combustible gas and melting the ash to form molten slagin a slagging combustion furnace, the slagging combustion furnacecomprising a primary combustion chamber, a secondary combustion chamberand a tertiary combustion chamber; trapping the molten slag on a wallsurface of the primary combustion chamber and flowing the trapped moltenslag downwardly into the secondary combustion chamber; flowing themolten slag on the wall surface of the secondary combustion chamber to aslag discharge groove and discharging the molten slag through the slagdischarge groove, a slag discharge port block disposed at a lowermostpart of the secondary combustion chamber having a slag discharge grooveat the primary combustion chamber side; trapping molten slag on a wallsurface of the tertiary combustion chamber from combustion gasintroduced into the tertiary combustion chamber, and then dischargingthe trapped molten slag through the slag discharge groove to the slagdischarge port; cooling and solidifying the molten slag discharged fromthe slag discharge groove; and drawing steam generated by the coolingand solidifying of the molten slag and combustion gas through the slagdischarge port of the secondary combustion chamber to form a mixed gas,and introducing the mixed gas to the tertiary combustion chamber.

[0037] According to the present invention, because the combustion gas isdrawn through the slag discharge port together with steam generated bycooling of slag and solidification of the slag, the slag discharge portand a portion around the slag discharge port can be prevented from beingcooled by the steam, and can be kept at a high temperature.

[0038] According to one aspect of the present invention, there isprovided a waste treatment method comprising: gasifying wastes toproduce a combustible gas containing ash in a fluidized-bed furnace;combusting the combustible gas and melting the ash to form molten slagin a slagging combustion furnace, the slagging combustion furnacecomprising a primary combustion chamber, a secondary combustion chamberand a tertiary combustion chamber; trapping the molten slag on a wallsurface of the primary combustion chamber and flowing the trapped moltenslag downwardly into the secondary combustion chamber; flowing themolten slag on the wall surface of the secondary combustion chamber to aslag discharge groove and discharging the molten slag through the slagdischarge groove, a slag discharge port block disposed at a lowermostpart of the secondary combustion chamber having the slag dischargegroove at the primary combustion chamber side; trapping molten slag on awall surface of the tertiary combustion chamber from combustion gasintroduced into the tertiary combustion chamber, and then flowing themolten slag on the wall surface of the tertiary combustion chamber tothe slag discharge port block and discharging the molten slag throughthe slag discharge groove; cooling the molten slag discharged throughthe slag discharge groove in a slag discharge chute; and detecting apressure differential between an interior of the secondary combustionchamber and an interior of the slag discharge chute; wherein when thepressure differential exceeds a set value, a secondary combustionchamber burner provided at the secondary combustion chamber is operatedto heat a portion around the slag discharge port.

[0039] According to the present invention, a pressure differentialbetween the interior of the slag discharge chute and the interior of thesecondary combustion chamber is detected, and if the pressuredifferential exceeds a set value, then an inclination of clogging of theslag discharge port by attachment of slag and solidification of the slagis judged, and the slag discharge port and a portion around the slagdischarge port are heated by a secondary combustion chamber burner toprevent the slag discharge port from being clogged.

[0040] According to one aspect of the present invention, there isprovided a waste treatment apparatus comprising: a fluidized-bed furnacefor gasifying wastes to produce a combustible gas containing ash; aslagging combustion furnace for combusting the combustible gas andmelting the ash to form molten slag, the slagging combustion furnacecomprising a primary combustion chamber, a secondary combustion chamber,a tertiary combustion chamber, and a slag discharge port block at alowermost part of the secondary chamber and having a slag dischargegroove at the primary combustion chamber side; wherein the molten slagis trapped on a wall surface of the primary combustion chamber and thetrapped molten slag flows downwardly into the secondary combustionchamber, the molten slag flows on the wall surface of the secondarycombustion chamber to the slag discharge groove and the molten slag isdischarged from the slag discharge groove, molten slag is trapped on awall surface of the tertiary combustion chamber from combustion gasintroduced into the tertiary combustion chamber, and then the trappedmolten slag flows downwardly to the slag discharge port block and isdischarged from the slag discharge groove; a slag discharge chutedisposed below the slag discharge port block for cooling the molten slagdischarged from the slag discharge groove; and a pressure instrument fordetecting a pressure differential between an interior of the secondarycombustion chamber and an interior of the slag discharge chute; whereinwhen the pressure differential between the interior of the secondarycombustion chamber and the interior of the slag discharge chute exceedsa set value, a secondary combustion chamber burner provided at thesecondary combustion chamber is operated to heat a portion around theslag discharge port.

[0041] According to the present invention, a pressure differentialbetween the interior of the slag discharge chute and the interior of thesecondary combustion chamber is detected, and if the pressuredifferential exceeds a set value, then an inclination of clogging of theslag discharge port by attachment of slag and solidification of the slagis judged, and the slag discharge port and a portion around the slagdischarge port are heated by a secondary combustion chamber burner toprevent the slag discharge port from being clogged.

BRIEF DESCRIPTION OF DRAWINGS

[0042]FIG. 1 is a schematic view showing a conventional gasification andslagging combustion system;

[0043]FIG. 2 is a schematic view of the conventional slagging combustionfurnace;

[0044]FIG. 3 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace in an example;

[0045]FIG. 4 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace in another example;

[0046]FIG. 5 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace according to the present invention;

[0047]FIGS. 6A through 6C are views showing a slag discharge port block,and FIG. 6A is a cross-sectional view (taken along line VI_(A)-VI_(A) ofFIG. 6B), FIG. 6B is a plan view, and FIG. 6C is a cross-sectional view(taken along line VI_(c)-VI_(c) of FIG. 6B);

[0048]FIG. 7 is a view showing a slag discharge port block of a slaggingcombustion furnace according to an example of the present invention;

[0049]FIG. 8 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace according to the present invention;

[0050]FIG. 9A is a cross-sectional view of a slag discharge port blockshown in FIG. 8 (a cross-sectional view taken along line IX_(A)-IX_(A)of FIG. 9B), and FIG. 9B is a plan view of the slag discharge port blockshown in FIG. 8;

[0051]FIG. 10 is a view showing a slag discharge port of a slaggingcombustion furnace according to another embodiment of the presentinvention;

[0052]FIG. 11 is an enlarged cross-sectional view showing an essentialpart of FIG. 10;

[0053]FIG. 12 is a view showing a slag discharge port of a slaggingcombustion furnace according to another embodiment of the presentinvention;

[0054]FIG. 13A is a cross-sectional view showing the slag dischargeport, and FIG. 13B is a plan view;

[0055]FIG. 14 is a view showing a slagging combustion furnace accordingto still another embodiment of the present invention;

[0056]FIGS. 15A through 15C are views showing the slag discharge portblock, and FIG. 15A is a perspective view of the slag discharge portblock, FIG. 15B is a cross-sectional view taken along line XV_(B)-XV_(B)of FIG. 15A, and FIG. 15C is a cross-sectional view taken along lineXV_(C)-XV_(C) of FIG. 15A;

[0057]FIG. 16 is an enlarged cross-sectional view showing an essentialpart of FIG. 14;

[0058]FIGS. 17A and 17B are cross-sectional views showing the manner inwhich molten slag flows through the slag discharge port; and

[0059]FIG. 18 is a view showing a slagging combustion furnace accordingto still another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0060] Embodiments of the present invention will be described below withreference to the drawings.

[0061]FIG. 5 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace according to the present invention. Asshown in FIG. 5, a slag discharge port block 22 is provided at thefurnace bottom between the secondary combustion chamber 12 and thetertiary combustion chamber 13 in the slagging combustion furnace 10.Reference numeral 23 represents water tubes 23 provided under the slagdischarge port block 22.

[0062]FIGS. 6A through 6C show the slag discharge port block 22, andFIG. 6A is a cross-sectional view (taken along line VIA-VIA of FIG. 6B),FIG. 6B is a plan view, and FIG. 6C is a cross-sectional view (takenalong line VI_(c)-VI_(c) of FIG. 6B). The slag discharge port block 22is made of refractory material which is resistant to a thermal wear anda high temperature. For example, the refractory material comprises ahigh chromium refractory material containing chromium of 60% or more.The slag discharge port block 22 has a slag discharge port 17 at thecentral portion thereof. The upper surface 22 a of the slag dischargeport block 22 is formed into a slant surface which is inclineddownwardly toward the slag discharge port 17, and an innercircumferential surface 22 c constituting an inner wall surface of theslag discharge port 17 is formed into a vertical surface.

[0063] In the inner circumferential surface 22 c of the slag dischargeport block 22 constituting the inner wall surface of the slag dischargeport 17, the height h₁ at the upstream side (the arrow C side) of a flowof the combustion gas 16 is higher than the height h₂ at the downstreamside (the arrow D side) of the flow of the combustion gas 16 (h₁>h₂).The slag discharge port block 22 has a slag discharge groove 22 d formedin the upper surface 22 a such that the slag discharge groove 22 dextends from the outer periphery at the upstream side of the flow of thecombustion gas 16 to the slag discharge port 17. The width of the slagdischarge groove 22 d is wider at the outer circumferential side than atthe slag discharge port 17 side, and the slag discharge groove 22 d hasa substantially semicircular cross section.

[0064] In the case where the slag discharge port block 22 having theabove structure is provided at the opening portion formed at the furnacebottom between the secondary combustion chamber 12 and the tertiarycombustion chamber 13, the combustion gas 16 flowing from the secondarycombustion chamber 12 to the tertiary combustion chamber 13 flows intothe upper surface 22 a of the slag discharge port block 22 from theupstream side (the arrow C side) of the slag discharge port, and flowsthrough a location above the slag discharge port 17 to the downstreamside (the arrow D side) of the slag discharge port. As described above,in the inner circumferential surface 22 c, the height h₁ at the upstreamside is higher than the height h₂ at the downstream side (h₁>h₂).Therefore, as shown in FIG. 6A, an inclination angle of the uppersurface 22 a at the upstream side is set such that the combustion gas 16which has passed through the location above the slag discharge port 17does not collide with the inner circumferential surface 22 c, and hencethe combustion gas 16 flows along the upper surface 22 a at thedownstream side into the tertiary combustion chamber 13. Therefore, thecombustion gas 16 is prevented from being flowing into the slagdischarge port 17.

[0065] Because the slag discharge port block 22 is composed of adistinct member different from the furnace wall of the slaggingcombustion furnace, the slag discharge port block 22 is not cooledexcessively by the water tubes 23, and thus the molten slag 20 is notadhered to the slag discharge port block and is not solidified thereondue to an excessive cooling. Further, since the slag discharge groove 22d extending from the outer periphery at the upstream side to the slagdischarge port 17 is formed in the upper surface 22 a of the slagdischarge port block 22, the molten slag 20 flowing downwardly on theinner wall surface of the slagging combustion furnace 10 collects in theslag discharge groove 22 d, and then flows into the slag discharge port17. Thus, the molten slag 20 is prevented from being adhered to thesurface of the slag discharge port block 22 and being solidifiedthereon. The number of the slag discharge grooves 22 d may be one orplural.

[0066] The length of the inner circumferential surface 22 c of the slagdischarge port block 22 constituting the inner wall surface of the slagdischarge port 17 is preferably short in view of preventing the moltenslag 20 from being adhered thereto or solidified thereon. For example,as shown in FIG. 7, the height h of the slag discharge port block 22should be short.

[0067]FIG. 8 is a view showing a slag discharge port and its vicinity ofa slagging combustion furnace according to the present invention. FIG.9A is a cross-sectional view of the slag discharge port block(cross-sectional view taken along line IX_(A)-IX_(A) of FIG. 9B), andFIG. 9B is a plan view of the slag discharge port block 22 shown in FIG.8. As shown in FIGS. 9A and 9B, the slag discharge port block 22 has anupper surface 22 a which is a slant surface inclined downwardly towardthe outer circumferential portion thereof. A slag discharge groove 22 dextending from an outer periphery at the upstream side of a flow of thecombustion gas to the slag discharge port 17 is formed in the uppersurface 22 a.

[0068] Since the upper surface 22 a of the slag discharge port block 22is formed into the slant surface which is inclined downwardly toward theouter periphery of the slag discharge port block 22, molten slagattached to the upper surface 22 a is entirely collected at the outercircumferential portion of the slag discharge port block 22. Then, thecollected molten slag flows together with molten slag 20 flowing on theinner wall surface of the secondary combustion chamber 12 and thetertiary combustion chamber 13 of the slagging combustion furnace 10into the connecting portion between the inner wall surface of theslagging combustion furnace 10 and the outer circumferential surface ofthe slag discharge port block 22. Thereafter, the molten slag 20 flowsthrough the slag discharge groove 22 d into the slag discharge port 17,and falls down through the slag discharge port 17. Thus, the molten slag20 is prevented from being adhered to the surface of the slag dischargeport block 22 and being solidified thereon. The number of the slagdischarge grooves 22 d may be one or plural.

[0069] On the other hand, the combustion gas 16 which has flowed intothe upper surface 22 a at the upstream side of the slag discharge portblock 22 moves toward the slag discharge port 17 in an upward flow (seeFIG. 9A). Thus, the combustion gas 16 flows through a location above theslag discharge port 17, and hence the combustion gas 16 is preventedfrom flowing into the slag discharge port 17. Further, because the uppersurface of the slag discharge port block is formed into a slant surfacewhich is inclined downwardly toward the outer periphery of the slagdischarge port block, molten slag attached to the upper surface isentirely collected at the outer circumferential portion of the slagdischarge port block, and molten slag flowing downwardly on the innerwall surface of the slagging combustion furnace is collected at theouter circumferential portion of the slag discharge port block. Then,the molten slag flows through the slag discharge groove 22 d into theslag discharge port 17, and falls down through the slag discharge port17. Thus, the molten slag is prevented from being adhered to the surfaceof the slag discharge port block and being solidified thereon.

[0070] Further, the slag discharge port block 22 is produced in advancefrom refractory material through a forming process and a drying processas a precast block in a plant. Thus, it is possible to employ refractorymaterial (for example, high chromium refractory material containingchromium of 60% or more) which is resistant to a thermal wear and a hightemperature. Further, if the slag discharge port block 22 comprises aplurality of block pieces, which have been produced through the aboveforming process and drying process, then production of the block pieces,and transportation of the block pieces are facilitated, and only damagedor broken block pieces can be replaced. Although the slag discharge portblock 22 comprises a circular disk in the above embodiment, the slagdischarge port block 22 may comprise an elliptical disk or a rectangularparallelepiped so as to fit the structure of the slagging combustionfurnace 10.

[0071]FIG. 10 is a view showing a slag discharge port of a slaggingcombustion furnace according to another embodiment of the presentinvention. As shown in FIG. 10, a slag discharge port 17 is provided atthe furnace bottom between the secondary combustion chamber 12 and thetertiary combustion chamber 13 of the slagging combustion furnace 10.The upper surface 17 b of the furnace bottom at an outer circumferentialportion around the slag discharge port 17 is formed into a slant surfacewhich is inclined downwardly toward the slag discharge port 17, and theheight h₁ of the inner wall surface of the slag discharge port 17 at theupstream side of a flow of the combustion gas 16 is higher than theheight h₂ of the inner wall surface of the slag discharge port 17 at thedownstream side of the flow of the combustion gas 16 (h₁>h₂).

[0072]FIG. 11 is an enlarged view showing an essential part of FIG. 10.As shown in FIG. 11, an inclination angle α of the upper surface 17 b atthe upstream side of the flow of the combustion gas 16, the height h₁ ofthe inner wall surface of the slag discharge port 17 at the upstreamside of the flow of the combustion gas 16, and the height h₂ at thedownstream side of the flow of the combustion gas 16 are set such thatthe combustion gas 16 flowing on the upper surface 17 b at the upstreamside of the slag discharge port 17 passes through a location above theslag discharge port 17, and reaches the upper surface 17 b at thedownstream side of the slag discharge port 17.

[0073] Because the inclination angle α of the upper surface 17 b at theupstream side of the slag discharge port 17, the height h₁ of the innerwall surface of the slag discharge port 17 at the upstream side, and theheight h₂ at the downstream side are set in the above-described manner,the combustion gas 16 which has flowed into the upper surface 17 b atthe upstream side of the slag discharge port 17 passes though a locationabove the slag discharge port 17 in a smooth stream without generating aturbulent flow at the location near the slag discharge port 17.Therefore, the flow of the combustion gas 16 does not affect adverselythe discharge state of the molten slag 20 flowing into the slagdischarge port 17. Further, the combustion gas 16 can be prevented frombeing discharged through the slag discharge port 17 to the outside ofthe furnace.

[0074]FIG. 12 is a view showing a slag discharge port and its vicinityof a slagging combustion furnace according to the present invention.FIG. 13A is a cross-sectional view showing the slag discharge port shownin FIG. 12, and FIG. 13B is a plan view showing the slag discharge portshown in FIG. 12. The upper surface 17 b of the furnace bottom at anouter circumferential portion around the slag discharge port 17 isformed into a slant surface which is inclined upwardly toward the slagdischarge port 17. A slag discharge groove 17 d extending from an outerperiphery at the upstream side of a flow of the combustion gas to theslag discharge port 17 is formed in the upper surface 17 b.

[0075] As described above, since the upper surface 17 b at the radiallyouter side of the slag discharge port 17 is formed into the slantsurface which is inclined upwardly toward the slag discharge port 17,the combustion gas 16 which has flowed into the upper surface 17 b atthe upstream side of the slag discharge port 17 moves toward the slagdischarge port 17 in an upward flow as shown in FIG. 13A. Thus, thecombustion gas 16 flows through a location above the slag discharge port17, and hence the combustion gas 16 is prevented from flowing into theslag discharge port 17. Further, because the upper surface 17 b at theouter circumferential portion around slag discharge port 17 is formedinto the slant surface which is inclined upwardly toward the slagdischarge port 17, molten slag 20 attached to the upper surface isentirely collected at the radially outer side of the slag discharge port17, and molten slag flowing downwardly on the inner wall surface of theslagging combustion furnace is collected at the radially outer side ofthe slag discharge port 17. Thus, the molten slag 20 is prevented frombeing adhered to the upper surface 17 b and being solidified thereon.

[0076] Further, in the case where a gasification and slagging combustionsystem according to the present invention comprises a gasificationfurnace for gasifying wastes to produce a gas containing ash andunburned carbon, and the slagging combustion furnace having the abovestructure, the gasification furnace may comprise an internal circulatingfluidized-bed gasification furnace, an external circulatingfluidized-bed gasification furnace, a kiln furnace, or the like.

[0077] Although the swirling-type slagging combustion furnace has beendescribed as a slagging combustion furnace, in the case where thepresent invention is characterized by the height of the slag dischargeport and/or the inclination angle of the upper surface around the slagdischarge port to prevent clogging of the slag discharge port of theslagging combustion furnace, the slagging combustion furnace is notlimited to the swirling-type slagging combustion furnace, and may be anytype of slagging combustion furnace.

[0078]FIG. 14 is a view showing a slagging combustion furnace accordingto another embodiment of the present invention. A slag discharge portblock 32 is disposed at the lowermost position of the secondarycombustion chamber, and a slag discharge groove 32 d is formed in theslag discharge port block 32 only at the primary combustion chamber 11side. FIGS. 15A through 15C show the slag discharge port block, and FIG.15A is a perspective view of the slag discharge port, FIG. 15B is across-sectional view taken along line XV_(B)-XV_(B) of FIG. 15A, andFIG. 15C is a cross-sectional view taken along line XV_(C)-XV_(C) ofFIG. 15A. As shown in FIGS. 15A through 15C, the slag discharge portblock 32 has the slag discharge groove 32 d which faces the primarycombustion chamber 11. The slag discharge port block 32 is disposed atthe bottom portion of the secondary combustion chamber 12 which is anend portion of the primary combustion chamber 11.

[0079] With this arrangement, as shown in FIG. 15A, molten slag 20 whichhas flowed on the inner wall surface of the slagging combustion furnace10 is collected at the location around the slag discharge port block 32,and then is discharged from the slag discharge groove 32 d. Because thedischarge of molten slag is concentratedly carried out by the slagdischarge groove 32 d, the molten slag is prevented from being cooled.Further, since the slag discharge groove 32 d is formed at the upstreamside (the primary combustion chamber side) of a flow of the combustiongas 16, part of the combustion gas 16 flows through the slag dischargegroove 32 d, thus keeping the molten slag 20 at a high temperature.

[0080]FIG. 16 is a view showing a detailed structure of the embodiment.FIGS. 17A and 17B are cross-sectional views showing the manner in whichmolten slag flows through the slag discharge port. As shown in FIGS. 14and 16, a line 40 is provided to connect a slag discharge chute 30 andthe tertiary combustion chamber 13, and a dust collector 41 and a fan 42are provided in the line 40. The slag discharge chute 30 constitutes awater quenching trough which cools molten slag 20 discharged through theslag discharge port by slag cooling water to form water-quenched slag.With the above arrangement, steam generated by cooling of molten slagand solidification of the slag is drawn from the slag discharge chute 30by the fan 42, and the combustion gas 16 which has passed through theslag discharge port 17 is drawn by the fan 42, thus forming a mixed gas.The mixed gas is fed to the tertiary combustion chamber 13. With thisarrangement, the molten slag can be smoothly discharged through the slagdischarge port 17 to the slag discharge chute 30 and then a waterreservoir 43 as shown in FIGS. 16 and 17A.

[0081] The supply position of the mixed gas which is drawn from the slagdischarge chute and is supplied to the slagging combustion furnace 10 isnot limited to the tertiary combustion chamber 13. Specifically, theline 40 can be constructed such that the line 40 connects the slagdischarge chute and at least one of a duct connecting the gasificationfurnace and the slagging combustion furnace, the primary combustionchamber, the secondary combustion chamber, the tertiary combustionchamber, and a flue provided upstream of a waste heat boiler. In thiscase, the dust collector 41 and the fan 42 are provided in the line 40,and a warm-up device may be further provided. With this arrangement, theslag discharge port 17 can be prevented from clogging and the moltenslag can be smoothly discharged through the slag discharge port 17 tothe slag discharge chute 30 and then the water reservoir 43 as shown inFIGS. 16 and 17A. With this arrangement, even if the mixed gas containsunburned carbon and the like, such unburned carbon and the like can becombusted and treated, and hence the mixed gas can be properly treated.In the case where the warm-up device is provided in the line 40, it isdesirable that the mixed gas is warmed up to a temperature of about 200°C. or higher, preferably about 300° C. or higher so as not to cause aremarkable temperature drop in the slagging combustion furnace, even ifthe mixed gas is supplied to the slagging combustion furnace.

[0082] Even if the above arrangement is employed, when the system isoperated for a long period of time, as shown in FIG. 14, even if themolten slag is prevented from being rapidly cooled locally, the moltenslag is attached to the slag discharge port and its vicinity of the slagdischarge block 32 or the like to form aggregated slag 21, and thus theslag discharge port 17 may be clogged with the slag (see FIG. 17B). Ifthis clogging of the slag discharge port occurs, the molten slag cannotbe discharged through the slag discharge port. Further, when the systemis operated for a long period of time, even if the slag dischargefunction is not completely lost, the slag discharge port tends to beclogged with the slag adhesion and solidification. Thus, it is importantto avoid an inclination of clogging of the slag discharge port becauseif there is an indication of decreasing an opening area of the slagdischarge port, the clogging of the slag discharge port rapidlyprogresses due to the following vicious circle. Specifically, thevicious circle is as follows: As the opening area of the slag dischargeport is reduced, draft resistance (pressure loss) of the combustion gas16 which passes through the slag discharge port is increased. Thus, theamount of combustion gas to be drawn is lowered, it is difficult to keepthe molten slag at a high temperature, and hence the opening area of theslag discharge port is further reduced. Therefore, an inclination ofclogging of the slag discharge port has to be avoided. Thus, it isextremely important to prevent the above problems from occurring for thepurpose of ensuring the slag discharge function for discharging moltenslag smoothly through the slag discharge port.

[0083] In order to achieve the above object, in an embodiment shown inFIG. 18, the pressure differential between the interior of the slagdischarge chute 30 and the interior of the secondary combustion chamber12 is detected by the pressure instrument 45, and if the pressuredifferential exceeds a set value, an inclination of clogging of the slagdischarge port is judged, and the slag discharge port and a portionaround the slag discharge port are heated by a secondary combustionchamber burner 46. For example, a signal indicative of a pressuredifferential measured by the pressure instrument 45 is sent to acontroller (not shown) through a first signal transmitting means. Thecontroller judges whether the pressure differential is equal to orlarger than a set value, and if the pressure differential is equal to orlarger than the set value, then the controller sends a starting signalfor starting the secondary combustion chamber burner 46 to the secondarycombustion chamber burner 46 through a second signal transmitting means.This arrangement can prevent the slag discharge port and a portionaround the slag discharge port from being clogged.

[0084] According to the present invention, the following excellenteffects can be obtained.

[0085] (1) Because a slag discharge port is formed by a replaceable slagdischarge port block which is a distinct member different from a furnacewall, the slag discharge port block can be produced in advance usingrefractory material having a high resistance to a thermal wear and ahigh temperature through a predetermined manufacturing process (forexample, a forming process and a drying process) in a plant. Thus, thenewly produced slag discharge port block is carried into the site wherethe slagging combustion furnace is placed, and the slag discharge portblock which has been damaged by melting or broken for some cause can beeasily replaced with the newly produced slag discharge port block.Further, since the slag discharge port block is composed of refractorymaterial (for example, high chromium refractory material) which isresistant to a thermal wear and a high temperature, the inner wall ofthe slag discharge port can be prevented from being damaged by meltingor being broken. Further, since the slag discharge port is formed by theslag discharge port block, the slag discharge port is not cooledexcessively by water tubes, unlike a conventional discharge port, thuspreventing molten slag from being adhered or being solidified.

[0086] (2) Because a slag discharge groove extending from an outerperiphery of the slag discharge port block at an upstream side of acombustion gas passage to the slag discharge port is formed in an uppersurface of the slag discharge port block, molten slag flowing downwardlyon the inner wall surface of the slagging combustion furnace flowsthrough the slag discharge groove into the slag discharge port, andfalls down through the slag discharge port. Thus, the discharge positionof the molten slag is fixed. Further, since the molten slag flowsconcentratedly, even if the scale of system or operational condition ofthe system is such that the amount of slag to be generated is small, themolten slag is less susceptible to being cooled. Thus, the molten slagis prevented from being adhered to the surface of the slag dischargeport block or being solidified thereon.

[0087] (3) Because the upper surface of the slag discharge port block isformed into a slant surface which is inclined downwardly toward the slagdischarge port, and the height of the inner wall of the slag dischargeport at the upstream side of a flow of the combustion gas is higher thanthe height of the inner wall of the slag discharge port at thedownstream side of the flow of the combustion gas, the combustion gaswhich has flowed into the upper surface of the slag discharge port blockat the upstream side of the flow of the combustion gas passes through alocation above the slag discharge port, and flows along the uppersurface of the slag discharge port at the downstream side of the slagdischarge port. Thus, since the combustion gas does not collide with theinner wall surface of the slag discharge port, the combustion gas can beprevented from flowing into the slag discharge port. Further, the gasstream near the slag discharge port is smoothed, and hence a fallposition of the discharged molten slag is not deviated.

[0088] (4) Because the upper surface of the slag discharge port block isformed into a slant surface which is inclined downwardly toward theouter periphery of the slag discharge port block, the combustion gaswhich has flowed into the upper surface of the slag discharge port blockat the upstream side of the flow of the combustion gas moves toward theslag discharge port in an upward flow. Thus, the combustion gas isprevented from flowing into the slag discharge port. Further, becausethe upper surface of the slag discharge port block is formed into theslant surface which is inclined downwardly toward the outer periphery ofthe slag discharge port block, molten slag attached to the upper surfaceis entirely collected at the outer circumferential portion of the slagdischarge port block, and molten slag flowing downwardly on the innerwall surface of the slagging combustion furnace is collected at theouter circumferential portion of the slag discharge port block. Then,the molten slag flows through the slag discharge groove into the slagdischarge port. Thus, the molten slag is prevented from being adhered tothe surface of the slag discharge port block or being solidifiedthereon.

[0089] (5) Since the slag discharge port block is composed of aplurality of block pieces, the slag discharge port block can be easilyproduced and can be easily transported. Further, even if the slagdischarge port block is damaged or broken, only the block piece whichhas been damaged or broken can be replaced. Thus, the replacement of theblock piece is facilitated.

[0090] (6) As a slagging combustion furnace of a gasification andslagging combustion system, by using any of the above slaggingcombustion furnaces, the slagging combustion furnace which exhibits theabove features can be constructed.

[0091] (7) Because the height of the inner wall of the slag dischargeport at the upstream side of the flow of the combustion gas is higherthan the height of the inner wall of the slag discharge port at thedownstream side of the flow of the combustion gas, the combustion gaswhich has flowed along the upper surface at the upstream side of theslag discharge port passes through a location above the slag dischargeport, and reaches the upper surface at the downstream side of the slagdischarge port. Thus, since the combustion gas flows smoothly withoutcausing the combustion gas to collide with the inner wall of the slagdischarge port and without generating a turbulent flow at the locationnear the slag discharge port, the flow of the combustion gas does notaffect adversely the discharge state of the molten slag.

[0092] (8) Because the combustion gas passes through a location abovethe slag discharge port, and a flow direction of the combustion gas ischanged by the upper surface at the downstream side of the slagdischarge port, the amount of the combustion gas flowing into the slagdischarge port can be greatly reduced.

[0093] (9) Because the upper surface at an outer circumferential portionaround the slag discharge port is formed into a slant surface which isinclined upwardly toward the slag discharge port, and the height of theinner wall of the slag discharge port and the inclination angle of theslant surface at the upstream side of the flow of the combustion gas areset such that the combustion gas flowing along the slant surface at theupstream side reaches the slant surface at the downstream side, thecombustion gas which has flowed into the upper surface at the upstreamside of the slag discharge port passes through a location above the slagdischarge port, and reaches the upper surface at the downstream side ofthe slag discharge port without causing the combustion gas to collidewith the inner wall of the slag discharge port and without generating aturbulent flow at the location near the slag discharge port, thecombustion gas flow smoothly and the flow of the combustion gas does notaffect adversely the discharge state of the molten slag.

[0094] (10) Because the upper surface at an outer circumferentialportion around the slag discharge port is formed into a slant surfacewhich is inclined upwardly toward the slag discharge port, thecombustion gas which has flowed into the upper surface at the upstreamside of the slag discharge port moves toward the slag discharge port inan upward flow. Thus, the combustion gas is prevented from flowing intothe slag discharge port.

[0095] (11) Because a slag discharge groove extending from a slantsurface at the upstream side of the flow of the combustion gas to theslag discharge port is formed in the upper surface at an outercircumferential portion around the slag discharge port, molten slagflowing downwardly on the inner wall of the slagging combustion furnaceflows through the slag discharge groove into the slag discharge port.Thus, the discharge position of the molten slag is fixed.

[0096] (12) Because molten slag flows concentratedly through a slagdischarge groove, even if the scale of system or operational conditionof the system is such that the amount of slag to be generated is small,the molten slag is less susceptible to being cooled. Thus, the moltenslag is prevented from being adhered to the surface of the radiallyouter portion of the slag discharge port or being solidified thereon.

[0097] (13) Because a slag discharge groove is formed only at theprimary combustion chamber side, the slag is concentratedly dischargedthrough the slag discharge groove to prevent the molten slag from beingcooled.

[0098] (14) Because the combustion gas which has passed through the slagdischarge port is drawn together with steam generated by cooling of slagand solidification of the slag, the slag discharge port and a portionaround the slag discharge port can be prevented from being cooled by thesteam, and can be kept at a high temperature.

[0099] (15) A pressure differential between the interior of the slagdischarge chute and the interior of the secondary combustion chamber isdetected, and if the pressure differential exceeds a set value, then aninclination of clogging of the slag discharge port by attachment of slagand solidification of the slag is judged, and the slag discharge portand a portion around the slag discharge port are heated by a secondarycombustion chamber burner to prevent the slag discharge port from beingclogged.

INDUSTRIAL APPLICABILITY

[0100] The present invention is applicable to a slagging combustionfurnace and a gasification and slagging combustion system for beingsupplied with a gas produced in a gasification furnace or the like andcontaining ash and unburned carbon, and combusting the supplied gas at ahigh temperature to melt ash into molten slag.

1. A slagging combustion furnace comprising: a combustion chamber forcombusting a combustible gas containing ash and melting said ash; and aslag discharge port for discharging molten slag produced by melting saidash; wherein said slag discharge port is formed by refractory materialwhich is replaceable.
 2. A slagging combustion furnace according toclaim 1, wherein said slag discharge port comprises an opening formed ata central portion of a slag discharge port block, and at least one slagdischarge groove extending from an outer peripheral portion of said slagdischarge port block at the upstream side of a flow of combustion gas tosaid slag discharge port is formed in an upper surface of said slagdischarge port block.
 3. A slagging combustion furnace according toclaim 2, wherein said upper surface of said slag discharge port block isa slant surface which is inclined downwardly toward said slag dischargeport, and an upper end of an outer wall forming said slag discharge portat the upstream side of said flow of said combustion gas is higher thanan upper end of said inner wall forming said slag discharge port at thedownstream side of said flow of said combustion gas.
 4. A slaggingcombustion furnace according to claim 2, wherein said upper surface ofsaid slag discharge port block is a slant surface which is inclineddownwardly toward an outer circumferential portion of said slagdischarge port block.
 5. A slagging combustion furnace according toclaim 1, wherein said slag discharge port block comprises a plurality ofblock pieces.
 6. A gasification and slagging combustion system,comprising: a gasification furnace for gasifying wastes to produce acombustible gas containing ash and unburned carbon; and a slaggingcombustion furnace for combusting said combustible gas containing saidash and said unburned carbon and melting said ash; wherein said slaggingcombustion furnace comprises a slagging combustion furnace according toclaim
 1. 7. A slagging combustion furnace comprising: a combustionchamber for combusting a combustible gas containing ash and melting saidash; and a slag discharge port for discharging molten slag produced bymelting said ash; wherein the height of an inner wall forming said slagdischarge port is higher at the upstream side of a flow of combustiongas than at the downstream side of said flow of said combustion gas. 8.A slagging combustion furnace according to claim 7, wherein an uppersurface at an outer circumferential portion around said slag dischargeport is a slant surface inclined upwardly toward said slag dischargeport, and at least one slag discharge groove extending to said slagdischarge port is formed in said slant surface at the upstream side ofsaid flow of said combustion gas.
 9. A waste treatment methodcomprising: gasifying wastes to produce a combustible gas containing ashin a fluidized-bed furnace; combusting said combustible gas and meltingsaid ash to form molten slag in a slagging combustion furnace, saidslagging combustion furnace comprising a primary combustion chamber, asecondary combustion chamber and a tertiary combustion chamber; trappingsaid molten slag on an inner wall surface of said primary combustionchamber and flowing said trapped molten slag downwardly into saidsecondary combustion chamber; flowing said molten slag on said innerwall surface of said secondary combustion chamber and discharging saidmolten slag through a slag discharge groove formed in a slag dischargeport block to a slag discharge port formed in said slag discharge portblock, said slag discharge port block being disposed at a lowermost partof said secondary combustion chamber, said slag discharge groove beingformed at said primary combustion chamber side; trapping molten slag onan inner wall surface of said tertiary combustion chamber fromcombustion gas introduced into said tertiary combustion chamber, andthen discharging said trapped molten slag through said slag dischargegroove to said slag discharge port block; and supplying said molten slagdischarged from said slag discharge groove to a water quenching troughand cooling said discharged molten slag in said water quenching trough.10. A waste treatment method comprising: gasifying wastes to produce acombustible gas containing ash in a fluidized-bed furnace; combustingsaid combustible gas and melting said ash to form molten slag in aslagging combustion furnace, said slagging combustion furnace comprisinga primary combustion chamber, a secondary combustion chamber and atertiary combustion chamber; trapping said molten slag on a wall surfaceof said primary combustion chamber and flowing said trapped molten slagdownwardly into said secondary combustion chamber; flowing said moltenslag on said wall surface of said secondary combustion chamber to a slagdischarge groove and discharging said molten slag through said slagdischarge groove, a slag discharge port block disposed at a lowermostpart of said secondary combustion chamber having said slag dischargegroove at said primary combustion chamber side; trapping molten slag ona wall surface of said tertiary combustion chamber from combustion gasintroduced into said tertiary combustion chamber, and then dischargingsaid trapped molten slag through said slag discharge groove to said slagdischarge port; cooling and solidifying said molten slag discharged fromsaid slag discharge groove; and drawing steam generated by said coolingand solidifying of said molten slag and combustion gas through said slagdischarge port of said secondary combustion chamber to form a mixed gas,and introducing said mixed gas to said tertiary combustion chamber. 11.A waste treatment method comprising: gasifying wastes to produce acombustible gas containing ash in a fluidized-bed furnace; combustingsaid combustible gas and melting said ash to form molten slag in aslagging combustion furnace, said slagging combustion furnace comprisinga primary combustion chamber, a secondary combustion chamber and atertiary combustion chamber; trapping said molten slag on a wall surfaceof said primary combustion chamber and flowing said trapped molten slagdownwardly into said secondary combustion chamber; flowing said moltenslag on said wall surface of said secondary combustion chamber to a slagdischarge groove and discharging said molten slag through said slagdischarge groove, a slag discharge port block disposed at a lowermostpart of said secondary combustion chamber having said slag dischargegroove at said primary combustion chamber side; trapping molten slag ona wall surface of said tertiary combustion chamber from combustion gasintroduced into said tertiary combustion chamber, and then flowing saidmolten slag on said wall surface of said tertiary combustion chamber tosaid slag discharge port block and discharging said molten slag throughsaid slag discharge groove; cooling said molten slag discharged throughsaid slag discharge groove in a slag discharge chute; and detecting apressure differential between an interior of said secondary combustionchamber and an interior of said slag discharge chute; wherein when saidpressure differential exceeds a set value, a secondary combustionchamber burner provided at said secondary combustion chamber is operatedto heat a portion around said slag discharge port.
 12. A waste treatmentapparatus comprising: a fluidized-bed furnace for gasifying wastes toproduce a combustible gas containing ash; a slagging combustion furnacefor combusting said combustible gas and melting said ash to form moltenslag, said slagging combustion furnace comprising a primary combustionchamber, a secondary combustion chamber, a tertiary combustion chamber,and a slag discharge port block at a lowermost part of said secondarychamber and having a slag discharge groove at said primary combustionchamber side; wherein said molten slag is trapped on a wall surface ofsaid primary combustion chamber and said trapped molten slag flowsdownwardly into said secondary combustion chamber, said molten slagflows on said wall surface of said secondary combustion chamber to saidslag discharge groove and is discharged from said slag discharge groove,molten slag is trapped on a wall surface of said tertiary combustionchamber from combustion gas introduced into said tertiary combustionchamber, and then said trapped molten slag flows downwardly to said slagdischarge port block and is discharged from said slag discharge groove;a slag discharge chute disposed below said slag discharge port block forcooling said molten slag discharged from said slag discharge groove; anda pressure instrument for detecting a pressure differential between aninterior of said secondary combustion chamber and an interior of saidslag discharge chute; wherein when said pressure differential betweenthe interior of said secondary combustion chamber and the interior ofsaid slag discharge chute exceeds a set value, a secondary combustionchamber burner provided at said secondary combustion chamber is operatedto heat a portion around said slag discharge port.
 13. A slaggingcombustion furnace according to claim 2, wherein said slag dischargeport block comprises a plurality of block pieces.
 14. A slaggingcombustion furnace according to claim 3, wherein said slag dischargeport block comprises a plurality of block pieces.
 15. A slaggingcombustion furnace according to claim 4, wherein said slag dischargeport block comprises a plurality of block pieces.
 16. A gasification andslagging combustion system, comprising: a gasification furnace forgasifying wastes to produce a combustible gas containing ash andunburned carbon; and a slagging combustion furnace for combusting saidcombustible gas containing said ash and said unburned carbon and meltingsaid ash; wherein said slagging combustion furnace comprises a slaggingcombustion furnace according to claim
 2. 17. A gasification and slaggingcombustion system, comprising: a gasification furnace for gasifyingwastes to produce a combustible gas containing ash and unburned carbon;and a slagging combustion furnace for combusting said combustible gascontaining said ash and said unburned carbon and melting said ash;wherein said slagging combustion furnace comprises a slagging combustionfurnace according to claim
 3. 18. A gasification and slagging combustionsystem, comprising: a gasification furnace for gasifying wastes toproduce a combustible gas containing ash and unburned carbon; and aslagging combustion furnace for combusting said combustible gascontaining said ash and said unburned carbon and melting said ash;wherein said slagging combustion furnace comprises a slagging combustionfurnace according to claim
 4. 19. A gasification and slagging combustionsystem, comprising: a gasification furnace for gasifying wastes toproduce a combustible gas containing ash and unburned carbon; and aslagging combustion furnace for combusting said combustible gascontaining said ash and said unburned carbon and melting said ash;wherein said slagging combustion furnace comprises a slagging combustionfurnace according to claim 5.